1. Field of the Invention
The present invention relates to a disc balancing device and a method thereof, and in particular to an improved disc balancing device which can balance an eccentric mass of a disc rotatably disposed at a driving source, and a method thereof.
2. Description of the Related Art
In general, a disc drive such as the HDD includes a housing consisting of a base and a cover, a disc positioned in the housing and rotated by a spindle motor at a high speed, and a head suspension assembly for storing data in the disc or reproducing the stored data. The head suspension assembly is positioned adjacent to the disc and controlled by a linear motor. Here, one end portion of the head suspension assembly supports a head. The movement of the head suspension assembly is precisely controlled.
On the other hand, the head suspension assembly is very sensitive to vibration or impact. When the head suspension assembly is considerably impacted, the head damages the disc surface. Especially, the precise control of the head suspension assembly is much influenced by vibration generated due to an eccentric mass of the disc in driving of the spindle motor. That is, when the vibrations are generated due to the eccentric mass of the disc, the head cannot precisely sense a track of the disc. Accordingly, when displacement of the rotated disc is varied due to the eccentric mass, it is impossible to precisely store and reproduce the data through the head.
This eccentric mass of the disc may be generated during the fabrication process of the disc. As shown in FIG. 1, the eccentric mass may also be generated due to an assembly tolerance when discs 5 and 6 are connected to a rotor 3. An exemplary method for balancing the eccentric mass will now be explained. Referring to FIG. 1, a plurality of discs 5 and 6 are positioned at the upper and lower portions of the rotor 3 of a spindle motor 1. Force F is applied to the outsides of the discs 5 and 6 in the symmetrical direction from the rotor 3. Therefore, the discs 5 and 6 are respectively adhered to the rotor 3 facing in the opposite direction. In this state, a clamping member 7 is connected to the rotor 3 to fix the discs 5 and 6 in place. This method is called a biasing method. As a result, the biasing method adjusts the eccentric mass of the disc resulting from an assembly tolerance. However, in the biasing method, the eccentric mass due to an assembly error can be corrected only when a plurality of discs are assembled. Conversely, it is impossible to correct the eccentric mass of a single disc itself. In addition, in the case that only one disc is installed, the biasing method cannot balance the disc.
Another exemplary disc balancing method will now be described with reference to FIG. 2. A clamp 7 having a plurality of holes 7a and the disc 6 are installed at the rotor 3. Thereafter, a sensing unit senses an eccentric position of the disc 6. A mass member 9 is inserted into the hole 7a corresponding to the eccentric position. The mass member 9 fixed to the hole 7a compensates for the eccentric mass of the disc 6. However, a few tens of mass members are required to be inserted into the holes 7a. Furthermore, the plurality of mass members require having different mass. Also, it is inconvenient for the operator to insert each mass member 9 into the hole 7a. Moreover, although various mass members are provided, there is a limit to the preciseness of control of the eccentric ass of the disc.